A 2-way radio is a radio that can both transmit and receive (a transceiver), unlike a broadcast receiver which only receives content. A two-way radio (transceiver) allows the operator to have a conversation with other similar radios operating on the same radio frequency (channel). Two-way radios are available in mobile, stationary base and hand-held portable configurations. Hand-held radios are often called walkie-talkies, handie-talkies, or just hand-helds.
Two-way radio systems usually operate in a half-duplex mode; that is, the operator can talk, or he can listen, but not at the same time. A push-to-talk or Press to Transmit button activates the transmitter; when it is released the receiver is active. A mobile phone or cellular telephone is an example of a two-way radio that both transmits and receives at the same time, i.e. in full-duplex mode. Full-duplex may be achieved by the use of two different frequencies or by frequency.
**Source: Wikipedia, the free encyclopedia**